In the manufacture of many pharmaceutical products such as pills or lozenges, candies such as "M&M's", small mechanical parts such as ball bearings, or electrical components such as resistors or capacitors, it is often desirable to imprint a trademark, indicia, or other information or intelligence on each item. These products share a common characteristic in that they are all pellet-like, being small, often round or rounded, oval, bulbous, cylindrical, or polygonal in shape. Examples of pellet-like items are pills, lozenges, capsules, tablets and caplets.
Imprinting indicia on a series of pellet-like items is conveniently accomplished by a machine which receives a large number of items in bulk, typically from a feed hopper or bin, orients the items to a uniform relative orientation, conveys the oriented items to a printing unit wherein the indicia are applied to each item and discharges the items for subsequent packaging. U.S. Pat. No. 2,859,689 to Ackley is a typical example of a pellet marking machine which performs the steps outlined above. Pellet-like items, seen in FIG. 2 of the '689 patent, designated "P", are loaded in bulk into the feed hopper 22 where the items are received by a rotating drum or cylinder roll 23. The drum has a multiplicity of concavities or recesses 33 in its outwardly facing surface formed in accordance with the shape and size of the pellet-like items being processed. The items P are received into the concavities 33 as the drum rotates clockwise beneath hopper 22, retained in the concavities by cylindrical retainer surface 50 as the drum rotates and released to an endless conveyor 24 located beneath the drum, the conveyor having a multiplicity of individual carrier bars 110. Carrier bars 110 have corresponding concavities matching the concavities 33 in drum 23, and conveyor 24 is synchronized with drum 23 so that the matching concavities on the drum and the conveyor line up as the drum rotates clockwise and the conveyor circulates counterclockwise. Items P drop from concavities 33 in drum 23 into the matching concavities in the endless conveyor 24 once the items are clear of retaining surface 50. The pellet-like items P are then conveyed to a printing roller 27 which has ink laden images of the indicia or intelligence to be imprinted on the items circumferentially arrayed on its peripheral surface. Printing roller 27 rotates clockwise in synchronization with endless conveyor 24 and contacts the pellet-like items P as they pass beneath the printing roller 27, applying the ink laden image to each pellet-like item. After passing beneath printing roller 27 the pellet-like items P are discharged from conveyor 24 as the conveyor rounds its drive sprocket and the carrier bars 110 are momentarily vertically oriented.
Although machines similar to that described in the '689 patent provide an effective means for reliably and rapidly marking pellet-like items with indicia, the machines lack a certain versatility in that such machines cannot readily be converted for processing different types of pellet-like items. In the recent past, pellet marking machine versatility was not a concern because there were a relatively limited number of pellet shapes and sizes in the marketplace and manufacturers by and large were satisfied with a dedicated machine for a particular product line. However, as the various industries, most notably pharmaceuticals, evolved over time, pellet marking machine versatility became more important. To remain competitive in the marketplace, pellet marking machines have been forced to evolve to keep up with the faster pace of technological change in product development, encapsulation methods, marking methods and packaging requirements, in addition to meeting the needs for greater efficiency and lower cost imposed by the highly competitive markets. In this context pellet marking machine versatility, as evidenced by the ability to process different types of pellet-like items, has come to the fore as the desirable characteristic which makes one pellet marking machine superior to another among the various industrial customers.
The lack of versatility of pellet marking machines as described in the '689 patent is in great part attributable to the means and the method by which the carrier bars are attached to the endless chain in forming the conveyor. If a pellet marking machine is to process different pellet-like items, the carrier bars must be easily interchangeable because the concavities in the carrier bars must be specifically matched in size and shape to the particular pellet-like item being processed. Matching the concavity to the item is important for efficient processing of the items by the machine. Items which are too large for their receiving concavities may tend to dislodge from the carrier bars due to machine vibration during operation. Such items will roll loose and uncontrolled on the conveyor and will not be arranged in the proper relation when passing beneath the printing roller to receive the imprinted intelligence. The items could be crushed between the printing roller and the conveyor and foul moving parts of the machine, perhaps causing a stoppage of the machine altogether. Items which are too small or the wrong shape for their concavities will not be reliably and consistently positioned on the conveyor. Items which are not consistently positioned and held within the concavities of the carrier bar will not have the indicia printed in a consistent, desired location during the imprinting step, resulting in unacceptable product. Items which lodge too deeply within a concavity may only receive a partial imprint of the indicia or intelligence, or may receive no imprint at all. Thus carrier bars with concavities ill matched to the pellet-like items will cause inefficient machine operation and costly product wastage.
If a machine is to be capable of processing many different types of pellet-like items, the ability to rapidly and easily replace the carrier bars suited for one item with carrier bars having concavities matched to a different item is important. Currently, in machines such as described in the '689 patent, the carrier bars 110 are bolted to link members 112 of the endless chain, as shown in FIGS. 7 and 8 of the '689 patent. Two or more bolts are used for each of scores of carrier bars. Bolting of carrier bars to the endless chain has traditionally been the only means used to attach the carrier bars. The use of bolts provides a means for adjusting the alignment of the carrier bars within the machine. Alignment of the carrier bars is important, as for any moving part on the machine, to ensure quiet, precision operation of the machine avoiding unwanted vibration and damaging contact with other moving or stationary parts. Thus to convert a machine from processing one item type to another requires that a technician unbolt each carrier bar from the endless chain, remove each carrier bar, replace each carrier bar with a different carrier bar, align each carrier bar within a given positional tolerance to travel over the conveyor path without impinging on other machine components, torque each mounting bolt to a desired level, and adjust the final alignment as required once the carrier bars are completely replaced. This process is tedious and time consuming, resulting in significant machine down time and consequent adverse effects on production efficiency during the change over. The process can also entail some risk to the technician, if for example, a nut is used to retain the bolt; then the technician must place his hand within the machine, often between moving and stationary parts, to thread the nut onto the bolt and hold the nut stationary with a tool, such as a wrench, when the bolt is torqued down. Accidental starting of the conveyor in this situation can have predictable calamitous results. Furthermore, the small retainer nuts could be dropped into the machine where they might lodge in gear teeth or other moving parts, jamming the machine.
An alternative method of changing the carrier bars is available whereby only the carrier bar over the master link of the endless chain is removed, and then the master link of each chain run is disengaged, opening the conveyor and allowing it to be removed from the machine as a complete unit. Although this method proceeds more quickly than the interchange method described above, the alternative method suffers from several distinct disadvantages. First, conveyor assemblies comprised of several hundred carrier bars and their associated conveyor chains are very heavy and require at least two technicians to lift from or lower into the machine. Second, such complete conveyor assemblies are unwieldly and therefore difficult to remove from or mount onto the machine. Third, complete conveyor assemblies are bulky and thus difficult to transport and store when not in use. Fourth, such assemblies tend to lose their alignment relative to the machine when removed and man-handled, and must be realigned when installed in a machine. Fifth, the alternative method is inapplicable if an endless belt is used instead of the endless chain.
Clearly, there is a need for improvement of the means and method by which carrier bars are attached and aligned within the pellet marking machine providing increased machine versatility, improved carrier bar alignment, safer machine maintenance methods, and more efficient machine operation and utilization.